EP0225193B1

EP0225193B1 - Spraying nozzle

Info

Publication number: EP0225193B1
Application number: EP19860309365
Authority: EP
Inventors: Robert Norman Borwick
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-11-29
Filing date: 1986-12-01
Publication date: 1990-08-22
Also published as: GB8529403D0; EP0225193A2; DE3673610D1; EP0225193A3

Description

The present invention relates to spraying nozzles. Such nozzles may be used with advantage in agriculture, amenity and forestry for spraying crops with fungicides, pesticides, herbicides, and the like, see e.g. GB-A-2157591.
According to the invention, there is provided a spraying nozzle comprising: a chamber containing an impingement surface, a liquid inlet for directing a liquid jet towards the impingement surface, an outlet, and inlet means for producing an air flow from the region of the liquid inlet generally towards the outlet; and a deflecting surface disposed downstream of the outlet and arranged to deflect atomised liquid out of the nozzle, characterised in that the impingement surface is disposed in the chamber between the liquid inlet and the outlet, the liquid inlet directs the liquid jet against the impingement surface so as to atomise the liquid, and the inlet means is arranged to direct air around the liquid jet towards the outlet so as to carry atomised liquid through the outlet.
Preferably the liquid inlet and the outlet are substantially coaxial. Preferably the air inlet means comprises a plurality of orifices disposed around the liquid inlet.
Preferably the chamber tapers inwardly towards the outlet. The chamber surface may be a surface of rotation, such as a frusto-conical surface. The air inlet means may be arranged to direct air along or adjacent the chamber surface.
The ratio of the cross-sectional areas of the liquid inlet and the outlet is preferably between 1:4 and 1:5. A ratio of approximately 1:4.35 has proved advantageous. The liquid inlet and the outlet may have circular cross-sections.
The deflecting surface may be inclined at an angle of between 65 and 85 degrees to the direction of liquid leaving the outlet. An angle in the region of 75 degrees is preferred and 75 degrees has proved advantageous in use.
Preferably the impingement surface is a polygonal (e.g. triangular) plate fixed at its apices to the chamber. When the chamber is a surface of rotation, the plate may be a symmetrically disposed equilaterally triangular plate. The air inlet means may comprise three orifices arranged to direct air jets at the respective gaps between the edges of the triangular plate and the chamber surface. The impingement surface may be convex towards the liquid inlet.
An agricultural spraying device may be provided by mounting a plurality of nozzles on a support and providing means for supplying liquid and air to the nozzles under pressure. The nozzles may be arranged in a line on the support with a spacing of about 50 centimetres between adjacent nozzles. The support may be arranged to carry the nozzles at a height of approximately 18 to 21 inches (approximately 45 to 52.5 centimetres) above a crop to be sprayed.
The invention will be further described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a part sectional view of a spraying nozzle constituting a preferred embodiment of the invention;
Figure 2 illustrates three of the component parts of the nozzle of Figure 1; and
Figure 3 illustrates an agricultural spraying arrangement using nozzles of the type shown in Figure 1.

The nozzle shown in Figure 1 comprises a liquid inlet connector 1 which is connected to a diaphragm check valve assembly 2. The check valve assembly 2 is connected by screw threading 3 to a first member 4. A nipple 5 is screw threaded to the first member 4 and is shown connected to an air line or pipe 6.
The first member 4 has an axial bore 7 which communicates with a liquid outlet of the assembly 2. The first member 4 further has an annular chamber 8 which communicates via a radial bore and a centre bore in the nipple 5 with the air line 6.
The first member 4 is connected to a second member 9 by screw threading 10. The second member 9 has an axial bore 11 which smoothly continues the bore 7 and ends in a liquid metering orifice 12.
A distribution plate 13 is disposed between the first and second members 4 and 9 and includes eight air distribution holes illustrated at 14 in Figure 2. The second member 9 has an annular chamber 15 which communicates with three through-bores 16. The bores 16 are inclined by an acute angle with respect to the bore 11 and surround equiangularly the bore 11.
The nozzle comprises a third member 17 fixed to the second member 9 by meas of a shouldered nut 18 screwed to the second member. The third member 17 defines a chamber 19 which tapers towards an outlet orifice 20. The chamber surface is frusto-conical in the nozzle shown in Figure 1.
A baffle plate 21 is provided in the chamber 19. The plate 21 is triangular and is fixed by welding or otherwise at its apices to the interior of the third member 17. The plate 21 is disposed between the liquid orifice 12 and the outlet orifice 20 so as to obscure the latter from the former. The plate 21, together with the chamber surface, defines three passageways between its respective edges and the chamber wall, and the air ducts provided by the bores 16 are directed at these passages.
The third member 17 provides a deflecting surface 22 against which droplets from the outlet orifice 20 are directed. The surface 22 is inclined at an angle of approximately 75° to the axis of the outlet orifice 20.
Figure 3 illustrates a possible application of the nozzles shown in Figures 1 and 2 to an agricultural crop spraying arrangement attached to an agricultural vehicle or tractor whose front and rear wheels are shown at 31 and 32, respectively. The arrangement comprises a spraying apparatus 33 mounted at the rear of the tractor and comprising a liquid tank 34, a pump 35 for pumping the liquid from the tank to the spraying nozzles (not shown), and a coupling 36 connecting the pump 35 to a power take-off 37 of the tractor. The sprayer 33 has outlets 38 connected via supply lines 39 to a system including pipes 40 and 41 for supplying liquid to the nozzles (not shown in Figure 3). This distribution system is mounted to booms 42 which are attached to a front loader of the tractor. The height of the booms 42 above a crop to be sprayed may therefore be adjusted by controlling the height of the front loader.
A set of V belts 43 transfers drive from a multiple V belt pulley mounted on an input shaft of the pump 35 to a further such pulley mounted on the shaft of an air compressor 44. The output of the air compressor 44 is connected via a pipe 45 to a diaphragm pressure regulator and T-connector 46. The outputs of the T-connector are connected to pipes 47 which in turn are connected to distribution pipes 48 mounted on the booms 42 for supplying air to the spraying nozzles.
The nozzles 1 are fixed to the booms 42 with a mutual spacing of approximately 50 centimetres. During normal operation, the nozzles spray crops from a height of approximately 21 inches (52.5 centimetres) above the top of the crop. Fixing of the nozzles is achieved by rigidly connecting them to the liquid distributing pipes 40 and 41 on the booms 42. The tubes 6 from the nozzles are connected to outlets on the air distribution pipes 48. Liquid under pressure and air under pressure are therefore supplied to each of the nozzles 1, which atomises the liquid in the following way.
Liquid passes along the ducts 7 and 11 and is emitted from the orifice 12 as a narrow jet. This jet strikes the baffle plate 21 and undergoes an initial atomisation as a result of this. Compressed air is emitted from the ducts 16 and entrains the atomised liquid, carrying it through the passages between the edges of the plate 21 and the surface of the chamber 19. The atomised liquid is thus ejected through the orifice 20 and strikes the surface 22 where final atomisation takes place and the flow is deflected downwardly in a fan- shaped spray.
The sizes of the orifices 12 and 20 together with the pressures of the air and liquid supplied to the nozzle affect the mean droplet size and the distribution of droplet sizes, and also affect the rate at which liquid is sprayed from the nozzle. Tests were performed to investigate the relationship between air and liquid pressures, orifice sizes, average droplet sizes, and rate of liquid output when used for spraying crops in a field. The results obtained are given below where VMD is volume medium diameter in microns (pm):
where the diameter of the orifice 12 was 0.028 inches (7.11 x 10^-4 m) and the diameter of the orifice 20 was 0.057 inches (1.45x10-³ m). The liquid output varied between 3 and 5 gallons per acre (3.4x10-³ and 5.6x10-³ Im-²) depending on pressures.
where the diameter of the orifice 12 was 0.35 inches 18.89x10^-4 m) and the diameter of the orifice 20 was 0.073 inches (1.85x10-³ m). The liquid output varied between 5 and 7 gallons per acre (5.6x10-³ and 7.9x10-³ Im-²) depending on pressures.
where the diameter of the orifice 12 was 0.040 inches (1.02x 10^-3 m) and the diameter of the orifice 20 was 0.0835 inches (2.12x10-³ m). The liquid output varied between 7 and 10 gallons per acre (7.9x10-3 and 1.12x10^-2 lm^-2) depending on pressures.
In addition, tests were performed to assess the distribution of droplet sizes, since it is desirable for the droplet diameters to be in the range from 100 to 350 microns (pm). The reason for this in some crop spraying is that droplet sizes above this limit do not increase the effectiveness of spraying and therefore waste liquid whereas droplet sizes below the minimum limit are too small and the spray tends to be carried away by the wind from its intended target. Using an air pressure of 20 Ibs per square inch (14060 Kgm-²) and a liquid pressure of 40 Ibs per square inch (28120 kgm-²) with the orifices 12 and 20 having diameters 0.035 and 0.073 inches (8.89x10^-4 and 1.85x 10-3 m), respectively, it was found that less than 15% of the droplets had diameters below the lower limit of 100 microns (um) and less than 15% of the droplets had diameters above the upper limit of 350 microns (pm).
The spray pattern produced by the nozzle has also been investigated and proved to have desirable characteristics. In particular, when using a plurality of nozzles spaced along a boom for instance as illustrated in Figure 3, it is desirable for the individual nozzle patterns to combine in such a way that a uniform spraying pattern is achieved along the length of the array of nozzles. It was found that the pattern produced by the nozzle could be readily overlapped with that from an adjacent nozzle without producing any peaks or troughs in the density of liquid sprayed at any point between the locations of the nozzles.
For some agricultural spraying purposes, a mean droplet diameter of about 200 microns (pm) seems to be optimum. As indicated in the tables hereinbefore, this may readily be achieved by selecting orifice diameters and air and liquid pressures, thus allowing the liquid output rate to be selected for a specific application. The nozzles provide such efficient spraying characteristics that the active ingredient in the liquid, such as a fungicide or pesticide, can be used at a much higher concentration i.e. with less water as diluent. It is therefore possible to spray greater areas, for a given liquid tank capacity, without having to reload with liquid than for conventional spraying arrangements.
It is therefore possible to produce a spraying system which allows the mean droplet size to be adjusted to an advantageous value and the spectrum of droplet sizes to be controlled within upper and lower limits so as to provide the most efficient droplet spectrum, so as to maximise any individual desired biological effect from the product being sprayed. Also, the droplet pattern produced by the nozzles can be adjusted to provide optimum return from any such product while giving optimum performance over a range of naturally occurring target areas, such as crops of different types.

Claims

1. A spraying nozzle comprising: a chamber containing an impingement surface, a liquid inlet for directing a liquid jet towards the impingement surface, an outlet, and inlet means for producing an air flow from the region of the liquid inlet generally towards the outlet; and a deflecting surface disposed downstream of the outlet and arranged to deflect atomised liquid out of the nozzle, characterised in that the impingement surface (21) is disposed in the chamber (19) between the liquid inlet (12) and the outlet (20), the liquid inlet (12) directs the liquid jet against the impingement surface (21) so as to atomise the liquid, and the inlet means (16) is arranged to direct air around the liquid jet towards the outlet (2) so as to carry atomised liquid through the outlet (20).

2. A nozzle as claimed in claim 1, characterised in that the liquid inlet (12) and the outlet (20) are substantially coaxial.

3. A nozzle as claimed in claim 1 or 2, characterised in that the inlet means comprises a plurality of orifices (16) disposed around the liquid inlet.

4. A nozzle as claimed in any one of the preceding claims, characterised in that the chamber (19) tapers inwardly towards the outlet (20).

5. A nozzle as claimed in claim 4, characterised in that the chamber surface is a surface of rotation.

6. A nozzle as claimed in claim 4 or 5, characterised in that the inlet means (16) is arranged to direct air along or adjacent the chamber surface.

7. A nozzle as claimed in any one of the preceding claims, characterised in that the ratio of the cross-sectional area of the liquid inlet (12) to the cross-sectional area of the outlet (20) is between 1:4 and 1:5.

8. A nozzle as claimed in any one of the preceding claims, characterised in that the deflecting surface (22) is inclined at an angle of between 65 and 85 degrees to the direction of atomised liquid leaving the outlet (20).

9. A nozzle as claimed in any one of the preceding claims, characterised in that the impingement surface (21) is provided by a polygonal plate fixed at its apices to the chamber (19).

10. A nozzle as claimed in claim 9, characterised in that the inlet means comprises a plurality of orifices (16) arranged to direct air jets at gaps between the edges of the plate (21) and the chamber surface.

11. A nozzle as claimed in any one of the preceding claims, characterised in that the impingement surface (21) is convex towards the liquid inlet (12).